1. Field of the Invention
An aspect of the present invention relates in general to a print medium feeding apparatus and an image forming apparatus using the same, and more specifically, to a print medium feeding apparatus for preventing double feeding, and an image forming apparatus using the same.
2. Description of the Related Art
An image forming apparatus is used for printing or scanning data that are generated internally or externally. For example, copy machines, printers, facsimiles, scanners, etc., are image forming apparatuses now broadly used. Each of these image forming apparatuses is equipped with an automatic paper feeding apparatus feeding paper sheets to output or receive data generated internally or externally.
The automatic paper feeding apparatus has a sheet separation member for feeding sheets one by one so that double feeding (i.e., more than one sheet of paper is fed at once) does not occur.
FIG. 1 is an enlarged detail view of a paper feeding unit used in a related art electrophotographic image forming apparatus 1, and FIG. 2 is an enlarged perspective view of a sheet separation member of FIG. 1.
Referring to FIGS. 1 and 2, the paper feeding unit includes a knockup plate 1 where paper sheets are stacked on, and a pickup roller 5 in contact with the upper side of the knockup plate 1 for picking up a sheet of printing paper 3 extending to the upper side of the knockup plate 1. A friction pad 7 is disposed between the pickup roller 5 and the front end of the knockup plate 1. The friction pad 7 comes in contact with the pickup roller 5 and supplies frictional force for separating the printing paper 3 sheet by sheet while the printing paper 3 is picked up by the pickup roller 5.
FIG. 2 is an enlarged view illustrating a state where the friction pad 7 is installed. Referring to FIGS. 1 and 2, there is a friction pad mount 9 supporting the friction pad 7. Thus, the friction pad 7 is mounted on the upper side of the friction pad mount 9. Here, a nip portion is formed between the friction pad 7 and the pickup roller 5.
Meanwhile, paper sheets of diverse sizes pass between the friction pad 7 and the pickup roller 5. Therefore, the friction pad 7 is made from optimum materials having a proper friction coefficient adaptive to different types of paper.
However, since the friction pad 7 is in contact with the pickup roller 5 at a constant pressure all the time, sometimes it fails to cope with the friction force of each of the paper sheets according to their properties. Consequently, printing papers are not separated sheet by sheet as they are supposed to, and double feeding or slipping occurs.
Moreover, as the pickup roller 5 is in direct contact with the friction pad 7, the friction pad 7 is easily worn out.
Although a large friction pad may be manufactured, this only gives rise to an increase in the material cost.